Why does Notepad open when I type www.google.com in IE ?

CNet describes a simple trick to run program files or open any local document from the Internet Explorer address bar by typing a valid web address like gmail.com or even wwww.google.com

Microsoft calls this IE shortcut a feature but it's just a matter of time before clever hackers exploit this "feature" and Microsoft will end up issuing a patch.

Here's the trick [harmless version] that you can even try on your own Windows XP computer.

• Right click on the Desktop and create a new Shortcut

• Type notepad.exe or calc.exe

• When you are asked to name the shortcut, say www.microsoft.com or www.google.com

Now start Internet Explorer, goto the address bar and type whatever web address you assigned to the desktop shortcut. Press Enter.

If the shortcut is then deleted--or the characters "http://" are added before the "www" in the browser address bar--then IE will once again connect to the Internet as expected.

Source: Microsoft: Shortcut 'trick' is legitimate feature